Method for charging and method for determining an end-of-charge criterion of a nickel-based battery

1. A method for charging an electrochemical nickel-based battery having a predetermined nominal capacity, the method comprising the following steps:

measuring a battery voltage at terminals of the battery;

measuring a temperature representative of the battery,

charging the battery with an intermittent and variable-current source of energy, the charging of the battery being stopped when the voltage measured at the terminals of the battery reaches a voltage threshold, the voltage threshold being dependent on the measured temperature such that an increase in the measured temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in each step, and the voltage threshold being representative of a capacity charged in the battery corresponding to a charging efficiency equal to or higher than 90%.

2. The method according to claim 1 , wherein the voltage threshold, depending on the measured temperature, is representative of a capacity charged in the battery comprised between 75% and 85% of a nominal capacity of the battery.

3. The method according to claim 1 , comprising two set values of temperature between which charging is allowed.

4. The method according to claim 1 , wherein the voltage threshold is constant within a range of temperature and different in various ranges of temperature.

5. The method according to claim 1 , wherein the voltage threshold is representative of an end-of-charge criterion obtained beforehand by the following steps:

plotting an efficiency curve representative of the charging efficiency according to the capacity charged in the battery,

selecting a value of maximum charge capacity corresponding to a break in slope of the efficiency curve,

plotting at least one voltage curve representative of the battery voltage according to the charged capacity, for a given temperature representative of the battery temperature, and

determining from the corresponding voltage curve, for each temperature, a voltage threshold representative of the end-of-charge criterion, corresponding to the value of maximum charge capacity.

6. The method according to claim 1 , wherein

the increase in the measured temperature from −10° C. to 40° C. decreases the voltage threshold:

from a first step to a second step when the measured temperature reaches a first temperature strictly superior to −10° C., and

from the second step to a third step when the measured temperature reaches a second temperature, the second temperature being strictly superior to the first temperature and strictly inferior to 40° C.

7. A method for determining an end-of-charge criterion of an electrochemical nickel-based battery and for charging the electrochemical nickel-based battery, the method comprising the following steps:

plotting, by a battery charger, an efficiency curve representative of a charging efficiency according to a capacity charged in the battery,

selecting, by the battery charger, a value of maximum charge capacity corresponding to a break in slope of the efficiency curve,

plotting, by the battery charger, at least one voltage curve representative of a battery voltage according to the charged capacity, for a given temperature representative of a battery temperature,

determining, by the battery charger, from the corresponding voltage curve, for each temperature, a voltage threshold representative of the end-of-charge criterion such that an increase in the temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in each step, and the voltage threshold corresponding to the value of maximum charge capacity, and

charging the electrochemical nickel-based battery based on the end of-charge-criterion such that the electrochemical nickel-based battery is charged at the corresponding voltage curve based on a measured temperature of the electrochemical nickel-based battery.

8. The method according to claim 7 , comprising generating a correlation table comprising several ranges of temperatures, each one being associated with a different voltage threshold.

9. The method according to claim 7 , wherein, the efficiency curve being a histogram representative of the charging efficiency according to ranges of charged capacity, the value of maximum charge capacity is included in a last range having a charging efficiency higher than 90%.

10. The method according to claim 9 , wherein the value of maximum charge capacity corresponds to the lower limit of the last range.

11. A method for charging an electrochemical nickel-based battery having a predetermined nominal capacity, the method comprising the following steps:

measuring a battery voltage at terminals of the battery;

measuring a temperature representative of the battery,

charging the battery with an intermittent and variable-current source of energy, the charging of the battery being stopped when the voltage measured at the terminals of the battery reaches a voltage threshold, the voltage threshold being dependent on the measured temperature such that an increase in the measured temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in each step on a temperature interval superior or equal to 5° C., and the voltage threshold being representative of a capacity charged in the battery corresponding to a charging efficiency equal to or higher than 90%.

12. A method for determining an end-of-charge criterion of an electrochemical nickel-based battery and for charging the electrochemical nickel-based battery, the method comprising the following steps:

plotting, by a battery charger, an efficiency curve representative of a charging efficiency according to a capacity charged in the battery,

selecting, by the battery charger, a value of maximum charge capacity corresponding to a break in slope of the efficiency curve,

plotting, by the battery charger, at least one voltage curve representative of a battery voltage according to the charged capacity, for a given temperature representative of a battery temperature,

determining, by the battery charger, from the corresponding voltage curve, for each temperature, a voltage threshold representative of the end-of-charge criterion such that an increase in the temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in each step on a temperature interval superior or equal to 5° C., and the voltage threshold corresponding to the value of maximum charge capacity, and

charging the electrochemical nickel-based battery based on the end of-charge-criterion such that the electrochemical nickel-based battery is charged at the corresponding voltage curve based on a measured temperature of the electrochemical nickel-based battery.

13. A method for charging an electrochemical nickel-based battery having a predetermined nominal capacity, the method comprising the following steps:

measuring a battery voltage at terminals of the battery;

measuring a temperature representative of the battery,

charging the battery with an intermittent and variable-current source of energy, the charging of the battery being stopped when the voltage measured at the terminals of the battery reaches a voltage threshold, the voltage threshold being dependent on the measured temperature such that an increase in the measured temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in a first step from 40° C. to 0° C., a second step from 0° C. to −5° C., and a third step from −5° C. to −10° C., and the voltage threshold being representative of a capacity charged in the battery corresponding to a charging efficiency equal to or higher than 90%.

14. A method for determining an end-of-charge criterion of an electrochemical nickel-based battery and for charging the electrochemical nickel-based battery, the method comprising the following steps:

plotting, by a battery charger, an efficiency curve representative of a charging efficiency according to a capacity charged in the battery,

selecting, by the battery charger, a value of maximum charge capacity corresponding to a break in slope of the efficiency curve,

plotting, by the battery charger, at least one voltage curve representative of a battery voltage according to the charged capacity, for a given temperature representative of a battery temperature,

determining, by the battery charger, from the corresponding voltage curve, for each temperature, a voltage threshold representative of the end-of-charge criterion such that an increase in the temperature from −10° C. to 40° C. decreases the voltage threshold in steps, the voltage threshold being constant in a first step from 40° C. to 0° C., a second step from 0° C. to −5° C., and a third step from −5° C. to −10° C., and the voltage threshold corresponding to the value of maximum charge capacity, and

charging the electrochemical nickel-based battery based on the end of-charge-criterion such that the electrochemical nickel-based battery is charged at the corresponding voltage curve based on a measured temperature of the electrochemical nickel-based battery.